As mobile terminal devices are popularized, the demand for charging speed for the mobile devices becomes higher accordingly. The users' experience will be improved greatly if an effect in which the mobile devices are charged with the maximum capacity can be realized when different charging source terminals are used. But at present, there are many and various charging standards such as USB BC1.2, USB Type-C, Apple MFi and Samsung, which are not compatible with each other completely, so when the charging source terminals complying with various standards are connected to the mobile devices, the maximum charging capacity cannot be realized, and the mobile devices can only be charged with less current or cannot be charged completely. This is especially obvious for Apple mobile devices. When an Apple mobile device is inserted into a charging source terminal not complying with the Apple MFi standard, it cannot regulate the load capacity according to the Apple MFi standard and only will be charged with a little current, which lengthens the charging time. Here the Apple devices refer to Apple mobile devices such as iPhone and iPad, MFi stands for Made for iPhone, and Apple MFi standard refers to a standard intended to improve interoperability between the iPhone and iPad and accessary devices. In summary, it is in need of an intermediary between the charging source terminal and the mobile device to make the various charging standards compatible with each other.